Biology subjects

Parekh, D.

Publications and source records attributed to Parekh, D..

7 recordsLinked to original sources

bioRxiv2026

Macrophage Phagocytic Impairment is associated with Dysbiosis of the Respiratory Microbiome in Frail older adults

Advanced age and frailty are risk factors for pulmonary infections, which are the leading cause of death in older adults. The mechanism behind increased susceptibility to infection is poorly understood, but interactions between innate immunity and the respiratory microbiome may be implicated. We investigated changes to monocyte-derived macrophage function, and the respiratory microbiome in healthy young adults, healthy older adults, and frail older adults. We found that macrophage phagocytosis and efferocytosis is impaired in frail older adults, associated with elevated pro-inflammatory cytokine secretion and a failure to regulate expression of phagocytic receptors CD14 and CD36. Pre-treatment of macrophages with a PPAR{gamma} agonist restored phagocytosis, implicating this pathway in cellular dysfunction. Accompanying respiratory microbiome showed reduced bacterial diversity and richness in older adults, which was more advanced in frail older adults. These results are consistent with a macrophage predation defect in the lungs during frailty which may impact bacterial diversity, and may be improved via manipulation of the PPAR{gamma} pathway. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=139 SRC="FIGDIR/small/703495v1_ufig1.gif" ALT="Figure 1"> View larger version (21K): org.highwire.dtl.DTLVardef@1c53e8forg.highwire.dtl.DTLVardef@8e34bcorg.highwire.dtl.DTLVardef@28345dorg.highwire.dtl.DTLVardef@185d93d_HPS_FORMAT_FIGEXP M_FIG C_FIG

immunology↗

bioRxiv2025

Stabilized Full-Length Measles Fusion Protein Elicits Potent Immunity and Protection In Vivo

Measles virus (MeV) is a highly contagious pathogen that causes significant morbidity and mortality in populations with low vaccination coverage. Infection typically leads to immune amnesia and, in rare cases, fatal neurological disease. While current live-attenuated vaccines are highly effective, they primarily elicit neutralizing antibodies against the hemagglutinin (H) glycoprotein, with a less robust response to the fusion (F) protein, a key protein for viral entry. To improve the immunogenicity of the F protein, we designed and characterized stabilized, prefusion MeV F protein antigens. We engineered both soluble ectodomains (FECTO) and full-length, membrane-embedded proteins (FFL) with mutations that confer thermal stability. Cryo-electron microscopy confirmed that these engineered antigens faithfully maintain the native prefusion conformation. When evaluated in a cotton rat model, immunization with either FECTO or FFL constructs induced neutralizing antibodies and elicited protection against viral challenge. The most stable full-length construct (FFL 3M) elicited a more potent neutralizing antibody response than its ectodomain counterpart. Importantly, no evidence of vaccine-enhanced respiratory disease was observed. These findings establish that a thermostable, full-length F protein is a superior immunogen to its soluble ectodomain. This work presents a promising candidate for next-generation, non-replicating measles vaccines intended to complement current vaccination strategies and provide a safe option for immunocompromised individuals and others who cannot receive live-virus vaccines. One-Sentence SummaryA prefusion-stabilized, full-length measles Fusion glycoprotein immunogen induces strong neutralizing responses and offers protection against challenge with wild-type virus.

immunology↗

bioRxiv2025

Uncovering the features of Measles-targeting human antibodies elicited by the MMR vaccine

Measles virus (MeV), a highly transmissible paramyxovirus, causes disease that can lead to severe complications and death, particularly in babies and young children. Deployment of the durable, highly effective, live-attenuated measles vaccine has saved an estimated 94 million lives in the past 50 years,1 yet the immunological explanation for this vaccines unique success and its landscape of antibody recognition remains unclear. Here we report the first panel of human monoclonal antibodies (mAbs) specific for the MeV hemagglutinin (H) and fusion (F) surface proteins, derived from the memory B cells of an MMR vaccinee. From over 100 cloned human mAbs, we mapped four major epitope clusters on H and another five major clusters on F, and structurally characterized 17 representative mAbs including one or more examples of each of the nine epitope clusters on the two surface antigens. We find that antibodies against both H and F can lead to potent virus neutralization and reduction of viral loads in vivo, including one mAb against F that reduces viral loads to below the limit of detection for all animals. High-resolution cryo-EM reveals contact sites of the most protective antibodies against both surface antigens. Discovery, characterization, and in vitro and in vivo success of these fully human mAbs now provide new avenues for prophylactic or therapeutic intervention against this re-emerging virus. HighlightsO_LIA large panel of Measles-specific monoclonal antibodies was isolated from a human MMR vaccinee, years after vaccination. C_LIO_LIStructural and biochemical mapping paints a landscape of antibody recognition with nine major competition groups, including four major sites on Hemagglutinin (H) and five on the fusion protein (F). C_LIO_LIAntibodies against both H and F confer in vitro neutralization and in vivo protection, including, in one case, undetectable viral load after antibody treatment. C_LIO_LIThe most protective H-specific mAbs, 4D08 and 1C08, target the receptor-binding site and the F-proximal outside of the H dimer, and likely function by interfering with receptor binding and H-F interactions, respectively. C_LIO_LIThe most protective F-specific mAbs, 3A12 and 4F09, target the sides and apex of the prefusion F trimer, and likely function by locking F into its pre-fusion state C_LI

immunology↗

bioRxiv2024

A broadly-neutralizing antibody against Ebolavirus glycoprotein that potentiates the breadth and neutralization potency of other antibodies

Ebolavirus disease (EVD) is caused by multiple species of Ebolavirus. Monoclonal antibodies (mAbs) against the virus glycoprotein (GP) are the only class of therapeutic approved for treatment of EVD caused by Zaire ebolavirus (EBOV). Therefore, mAbs targeting multiple Ebolavirus species may represent the next generation of EVD therapeutics. Broadly reactive anti-GP mAbs were produced; among these, mAbs 11886 and 11883 were broadly neutralizing in vitro. A 3.0 [A] cryo-electron microscopy structure of EBOV GP bound to both mAbs shows that 11886 binds a novel epitope bridging the glycan cap (GC), 310 pocket and GP2 N-terminus, whereas 11883 binds the receptor binding region (RBR) and GC. In vitro, 11886 synergized with a range of mAbs with epitope specificities spanning the RBR/GC, including 11883. Notably, 11886 increased the breadth of neutralization by partner mAbs against different Ebolavirus species. These data provide a strategic route to design improved mAb-based next-generation EVD therapeutics.

immunology↗

bioRxiv2023

Intracellular Ebola Virus nucleocapsid assembly revealed by in situ cryo-electron tomography.

Filoviruses, including Ebola and Marburg viruses, cause hemorrhagic fevers with up to 90% lethality. The viral nucleocapsid is assembled by polymerization of the nucleoprotein (NP) along the viral genome, together with the viral proteins VP24 and VP35. We employed cryo-electron tomography of cells transfected with viral proteins and infected with model Ebola virus, to illuminate assembly intermediates as well as a 9[A] map of the complete intracellular assembly. This structure reveals a previously unresolved, third, and outer layer of NP complexed with VP35. The intrinsically-disordered-region together with the C-terminal domain of this outer layer of NP provides the constant-width between intracellular nucleocapsid bundles and likely functions as a flexible tether to the viral matrix protein in virion. A comparison of intracellular nucleocapsid with prior in-virion nucleocapsid structures reveals the nucleocapsid further condenses vertically in-virion. The interfaces responsible for nucleocapsid assembly are highly conserved and offer targets for broadly effective antivirals.

microbiology↗

bioRxiv2022

Structure of the Inmazeb cocktail and resistance to escape against Ebola virus

Monoclonal antibodies can provide important pre- or post-exposure protection against disease for those not yet vaccinated or in individuals that fail to mount a protective immune response after vaccination. A key concern in use of monotherapy monoclonal antibody products lies in the high risk of mutagenic escape. Inmazeb (REGN-EB3), a three-antibody cocktail against Ebola virus, demonstrated efficacy in lessening disease course and improving survival in a randomized, controlled trial. Here we present the cryoEM structure at 3.1 [A] of the Ebola virus glycoprotein, determined without symmetry averaging, in a simultaneous complex with eight Fab fragments of antibodies in the Inmazeb cocktail. This structure allows modeling of previously disordered portions of the glycan cap, maps the non-overlapping epitopes of Inmazeb, and illuminates the basis for complementary activities, as well as residues that are critical for resistance to escape by each component of this cocktail and other clinically relevant antibodies. We also provide direct evidence that, unlike monotherapy treatments, including those targeting conserved epitopes, the Inmazeb protects against the rapid emergence of EBOV escape mutants and supports the benefit of the combination approach.

biophysics↗

bioRxiv2022

Glycan shield of the ebolavirus envelope glycoprotein GP

The envelope glycoprotein GP of the ebolaviruses is essential for host cell attachment and entry. It is also the primary target of the protective and neutralizing antibody response in both natural infection and vaccination. GP is heavily glycosylated with up to 17 predicted N-linked sites, numerous O-linked glycans in its disordered mucin-like domain (MLD), and three predicted C-linked mannosylation sites. Glycosylation of GP is important for host cell attachment to cell-surface lectins, as well as GP stability and fusion activity. Moreover, it has been shown to shield GP from neutralizing activity of serum antibodies. Here, we use mass spectrometry-based glycoproteomics to profile the site-specific glycosylation patterns of ebolavirus GP. We detect up to 16 unique O-linked glycosylation sites in the mucin-like domain, as well as two O-linked sites in the head and glycan cap domains of the receptor-binding GP1 subunit. Multiple O-linked glycans are observed at the S/T residues of N-linked glycosylation sequons, suggesting possible crosstalk between the two types of modifications. We also confirmed the presence of C-mannosylation at W288 in the context of trimeric GP. We find heterogenous, complex N-linked glycosylation at the majority of predicted sites as expected. By contrast, the two conserved sites N257 and N563 are enriched in unprocessed high-mannose and hybrid glycans, suggesting a role in host-cell attachment via DC-SIGN/L-SIGN. We discuss our findings in the context of antibody recognition to show how glycans contribute to and restrict neutralization epitopes. This information on how N-, O-, and C-linked glycans together build the heterogeneous glycan shield of GP can guide future immunological studies and functional interpretation of ebolavirus GP-antibody interactions.

biochemistry↗